Centralizes logic to validate complex editors, starts transitioning to new JSON error messages for complex editors, starts adding tests

src/Umbraco.Core/Models/Blocks/IBlockEditorDataHelper.cs

@@ -3,8 +3,12 @@ using System.Collections.Generic;
 
 namespace Umbraco.Core.Models.Blocks
 {
+    // TODO: Rename this, we don't want to use the name "Helper"
+    // TODO: What is this? This requires code docs
+    // TODO: This is not used publicly at all - therefore it probably shouldn't be public
     public interface IBlockEditorDataHelper
     {
+        // TODO: Does this abstraction need a reference to JObject? Maybe it does but ideally it doesn't
         IEnumerable<IBlockReference> GetBlockReferences(JObject layout);
         bool IsEditorSpecificPropertyKey(string propertyKey);
     }